问题：臃肿的镜像

传统做法把编译环境和运行环境混在一起，一个 Node.js 应用镜像动辄 800 MB+。

多阶段构建

# Stage 1: 构建
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY . .
RUN npm run build

# Stage 2: 运行（仅复制产物）
FROM node:20-alpine AS runner
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
EXPOSE 3000
CMD ["node", "dist/index.js"]

效果对比

单阶段：node:20 基础镜像约 950 MB；多阶段 + Alpine：最终镜像约 120 MB，减少 87%。